In paint manufacturing process, it is necessary to mix a plurality of ingredients or components such as pigment dispersions, colorants, concentrates, or other fluids or solid dispersions to produce a paint having desired physical properties such as color, opacity, saturation, and viscosity. Typically, the ingredients or components are mixed in a mixer or a series of mixers. A in-line mixer is a mixer that can continuously mix a plurality of ingredients or components based on a desired formulation. In a conventional in-line mixer, desired amounts of each of the ingredients or components are conveyed into the mixer according to the formulation via one or more inlets. The conveyed ingredients or components are then agitated by an impeller within a mixing chamber of the mixer. The mixed product is then conveyed out of the mixing chamber.
One example of such a conventional in-line mixer is described in detail in U.S. Pat. No. 6,637,926. Such a conventional in-line mixer, however, is not efficient enough to mix multiple ingredients due to the presence of dead volume within its mixing chamber. The impeller of such a conventional mixer occupies relatively a small portion of the mixing chamber volume. As a result, certain regions of the mixing chamber generate little or no turbulence even when the impeller is at high speed of rotation. Such little or no turbulence regions are known as dead volume. To reduce the dead volume, certain filler was introduced into the mixing chamber of the mixer. One example is described in aforementioned U.S. Pat. No. 6,637,926. However, introduction of such dead volume filler reduces desired useable volume in a mixing chamber. As a result, less amounts of ingredients can be mixed within the mixing chamber. Additionally, such dead volume fillers, contribute little or not at all to the mixing of the ingredients. These defects result in reduced productivity and mixing efficiency of such conventional in-line mixer.
Therefore a need still exists for an improved in-line mixer that not only provides higher turbulence, thereby increasing mixing efficiency but is also able to mix more amount of components than a conventional in-line mixer, such as that described in the patent mentioned earlier.